The present invention relates generally to equipment for mixing and dispensing settable slurries in which a setting agent is mixed with a settable slurry in a way that premature setting is prevented. More specifically, the present invention provides a slurry mixing and dispensing apparatus which is configured for continuously introducing a setting agent such as an accelerator into a flowing plaster slurry and thoroughly mixing the setting agent into the slurry without causing premature setting in the apparatus.
Plaster slurry equipment is used for the production of cast or molded plaster products such as, but not limited to, figurines, artistic novelties, household interior trim moldings and electric switch plates, trophy bases, dinnerware, industrial prototypes of manufactured products and the like. Existing plaster slurry processing techniques are limited to continuous processing equipment, and further, are limited to plaster and gypsum cement products where slurry viscosities are relatively low. Highly formulated gypsum cement products tend to be much more viscous in nature, and the existing equipment designs do not provide adequate mix processing required by the formulation (i.e. sift/soak/mix). Further, all known equipment is typically limited to a continuous output and are incapable of stop and go operation. Conventional mixing and dispensing equipment relies on volumetric powder metering and inadequate mixing using an open throat style progressive cavity pump. In such applications, reliance on relatively long feed hoses is necessary to obtain adequate mixing. Typically, production is presently based on manually mixed batches, and proceeds until the current batch of slurry is expended. Then production is suspended until another batch can be made. Batches of formulated slurry are continually agitated by mechanical mixers to avoid premature setting of the plaster slurry.
Another drawback of conventional slurry dispensing apparatus used for plaster slurries is a lack of adequate stop and start control for the dispensing of such slurries, such that material is wasted when the dispenser “weeps” slurry after output is meant to be stopped. Still another drawback of conventional plaster slurry dispensing apparatus is inadequate control over the dispensing of setting agents or accelerators. Incomplete mixing of the setting agent with the slurry causes uneven setting and inferior products. Premature setting in the dispensing apparatus causes clogged equipment, which requires disruption of the production line while the equipment is cleaned of the set plaster.
Accordingly, a first object of the present invention is to provide an improved slurry mixing and dispensing apparatus which is configured for shift-based rather than batch-based operation.
Another object of the present invention is to provide an improved slurry mixing and dispensing apparatus which is configured for minimizing the accumulation and premature setting of the gypsum slurry in the dispenser apparatus.
Still another object of the present invention is to provide an improved slurry mixing and dispensing apparatus which features controllable, relatively rapid stop and start operation.
Yet another object of the present invention to provide an improved slurry spray and/or dispensing apparatus which incorporates an accelerant into the slurry without internal clogging, and so that the accelerant is generally uniformly distributed in the slurry.
A further object of the present invention is to provide an improved slurry spray and/or dispensing apparatus which emits or ejects the slurry at a relatively constant rate to achieve a more uniform sprayed substrate.
A still further object of the present invention is to provide an improved slurry spray and/or dispensing apparatus in which the component parts such as pumps and valves are designed to accommodate the unique characteristics of plaster slurries for efficient industrial applications.
Yet a further object of the present invention is to provide an improved slurry spray and/or dispensing apparatus which features a pneumatically operated control and valve system for operator safety and for more controllable output of the sprayed slurry.